In diesel engines, the fuel is injected, atomized as finely as possible, into the combustion chamber of the engine. Piston pumps, in particular radial piston pumps of compact construction, are used for producing the high fuel injection pressure necessary for this purpose. Particularly for common-rail injection systems, use of a radial piston pump having a plurality of pump pistons permits the generation of constant high-pressure fuel supply.
In known radial piston pumps, three pump pistons are generally arranged in a pump housing in the radial direction around a camshaft. An eccentric cam having a central shaft, which is connected to the camshaft of an engine rotates with the camshaft. The rotation of the camshaft causes a polygon ring, which is arranged concentrically with respect to the eccentric cam, to execute a movement in the direction of the longitudinal axis of the pump piston and a transverse movement. The pump piston is pressed toward the polygon ring by a spring. The stroke movement is transmitted from the polygon ring to the pump piston via a piston-end disc. The transverse movement leads to a movement of the polygon ring relative to the piston-end disc. With the large forces, which occur on the basis of the high pressures, this transverse movement leads to increased wear between the piston-end disc and polygon ring. In addition, the high frictional forces decrease the efficiency of known piston pumps.
It is the object of the present invention to provide a high-pressure piston pump for pumping fuel, which is subjected only to low wear during operation.